<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, initial-scale=1.0">
		<title></title>
		<link rel="stylesheet" href="./Bootstrap4.6.1/css/bootstrap.css">
		<!-- 先引入jquery文件，再引入bootstrap文件 -->
		<script src="./Bootstrap4.6.1/js/jquery.js"></script>
		<script src="./Bootstrap4.6.1/js/bootstrap.bundle.js"></script>
		<style>
			
		</style>
	</head>
	<body>
		<div class="container">
			<div>aaaaaa</div>
			<span class="border text-primary p-5">001
			</span><span class="border-bottom text-muted bg-primary m-3">002
			</span><span class="border border-top-0 ">003
			</span><span class="border-left border-primary">004
			</span><span class="bg-danger rounded text-white">005
			</span><span class="bg-danger rounded-lg text-white-50">005</span>
			<hr>
			<div class="border">
				<div class="border w-50 mx-3">左右居中</div>
			</div>
		</div>
	</body>
</html>